(57) An automatic document conveying device (4) to be applied to an image processor (2) that has a transparent plate (8) disposed on the upper surface of a housing (6) so that a document to be processed is placed thereon. The automatic document conveying device comprises a document introduction portion (12), a main portion and a document delivery portion. The document introduction portion (12) includes an introduction portion frame member (18), a document table (20) that extends from the introduction portion frame member (18) toward the upstream side, a document introduction passage that extends from the document table (20) to the transparent plate (8) inside the introduction frame member (18), a document sending means for sending the document onto the document introduction passage from the document table, and a document introduction means for introducing onto the transparent plate the document sent onto the document introduction passage. The main portion includes a movable main portion frame member (70) that is mounted to move between a closed position for closing the transparent plate (8) and an open position for exposing the transparent plate (8) into view, and the document conveying means (74) that conveys the document along the transparent plate (8) when the movable main portion frame member (70) is at the closed position. The document conveying means (74) is constituted by a conveyer belt mechanism mounted on the movable main portion frame member. The document delivery portion (16) includes a delivery portion frame member (100), a document delivery passage defined within the delivery portion frame member, and a document delivery means that delivers the document onto the document receiving tray through the document delivery passage. The document delivery portion is provided with a document re-introduction passage that extends to the transparent plate being branched from the document delivery passage.